d-Xylulose Fermentation to Ethanol by Saccharomyces cerevisiae

We used commercial bakers' yeast (Saccharomyces cerevisiae) to study the conversion of d-xylulose to ethanol in the presence of d-xylose. The rate of ethanol production increased with an increase in yeast cell density. The optimal temperature for d-xylulose fermentation was 35 degrees C, and the optimal pH range was 4 to 6. The fermentation of d-xylulose by yeast resulted in the production of ethanol as the major product; small amounts of xylitol and glycerol were also produced. The production of xylitol was influenced by pH as well as temperature. High pH values and low temperatures enhanced xylitol production. The rate of d-xylulose fermentation decreased when the production of ethanol yielded concentrations of 4% or more. The slow conversion rate of d-xylulose to ethanol was increased by increasing the yeast cell density. The overall production of ethanol from d-xylulose by yeast cells under optimal conditions was 90% of the theoretical yield.     

Mechanism of Fermentation Conversion from Polyalcohol Fermentation to Ethanol Fermentation by Pichia miso

A possible mechanism of fermentation conversion is described from polyalcohol fermentation to ethanol fermentation by Pichia miso. Little alcohol dehydrogenase activity was found in polyalcohol-producing cells, whereas higher enzyme activity was induced by ethanol-producing cells. The fermentation conversion may be caused by the different levels of alcohol dehydrogenase activity between polyalcohol- and ethanol-producing cells. It was also shown that yeast growth was inhibited and that yeast cells were lysed by ethanol (at 6g/100ml) that accumulated in 24 hr.     

Specific Features of Fermentation of D-Xylose and D-Glucose by Xylose-Assimilating Yeasts

The ability to assimilate D-glucose and D-xylose was studied in 21 yeast species of the following genera: Candida, Kluyveromyces, Pachysolen, Pichia, and Torulopsis. All the cultures fermented D-glucose with the formation of ethanol. During the assimilation of D-xylose, ethanol was produced by P. stipitis and C. shehatae, whereas xylitol was produced by C. didensiae, C. intermediae, C. parapsilosis, C. silvanorum, C. tropicalis, K. fragilis, K. marxianus, P. guillermondii, and T. molishiama. The yeast P. tannophilus produced comparable amounts of both alcohols. The possible use of xylose-assimilating yeasts for the production of xy-litol and ethanol is discussed.     

Fermentation of d-Xylose to Ethanol by Genetically Modified Klebsiella planticola

d-Xylose is a plentiful pentose sugar derived from agricultural or forest residues. Enteric bacteria such as Klebsiella spp. ferment d-xylose to form mixed acids and butanediol in addition to ethanol. Thus the ethanol yield is normally low. Zymomonas spp. and most yeasts are unable to ferment xylose, but they do ferment hexose sugars to ethanol in high yield because they contain pyruvate decarboxylase (EC 4.1.1.1), a key enzyme that is absent from enteric bacteria. This report describes the fermentation of d-xylose by Klebsiella planticola ATCC 33531 bearing multicopy plasmids containing the pdc gene inserted from Zymomonas mobilis. Expression of the gene markedly increased the yield of ethanol to 1.3 mol/mol of xylose, or 25.1 g/liter. Concurrently, there were significant decreases in the yields of formate, acetate, lactate, and butanediol. Transconjugant Klebsiella spp. grew almost as fast as the wild type and tolerated up to 4% ethanol. The plasmid was retained by the cells during at least one batch culture, even in the absence of selective pressure by antibiotics to maintain the plasmid. Ethanol production was 31.6 g/liter from 79.6 g of mixed substrate per liter chosen to simulate hydrolyzed hemicellulose. The physiology of the wild-type of K. planticola is described in more detail than in the original report of its isolation.     

休哈塔假丝酵母发酵木糖制乙醇过程研究

木质纤维素原料水解产物的主要成分是葡萄糖和木糖,其中葡萄糖很容易发酵,致使木糖成为木质纤维素发酵的关键,休哈塔假丝酵母(Candida shehatae)1766是自然界木糖发酵性能较好的天然酵母之一。研究了发酵温度、发酵时间、接种量、初始pH值、摇床转速等因素对休哈塔假丝酵母1766发酵木糖生产乙醇的影响,由正交试验初步确定了休哈塔假丝酵母发酵木糖制乙醇工艺的适宜条件为好氧条件,发酵时间为2d,发酵温度为28℃,摇床转速为150r/min,初始pH值为5,此时乙醇收率最高可达68.62%。     

Fermentation of d-Xylose and l-Arabinose to Ethanol by Erwinia chrysanthemi

Erwinia spp. are gram-negative facultative anaerobes within the family Enterobacteriacae which possess several desirable traits for the conversion of pentose sugars to ethanol, such as the ability to ferment a broad range of carbohydrates and the ease with which they can be genetically modified. Twenty-eight strains of Erwinia carotovora and E. chrysanthemi were screened for the ability to ferment d-xylose to ethanol. E. chrysanthemi B374 was chosen for further study on the basis of its superior (4%) ethanol tolerance. We have characterized the fermentation of d-xylose and l-arabinose by the wild type and mutants which bear plasmids containing the pyruvate decarboxylase gene from Zymomonas mobilis. Expression of the gene markedly increased the yields of ethanol (from 0.7 up to 1.45 mol/mol of xylose) and decreased the yields of formate, acetate, and lactate. However, the cells with pyruvate decarboxylase grew only one-fourth as fast as the wild type and tolerated only 2% ethanol. Alcohol tolerance was stimulated by the addition of yeast extract to the growth medium. Xylose catabolism was characterized by a high saturation constant K(s) (4.5 mM).     

Direct Fermentation of d-Xylose to Ethanol by Kluyveromyces marxianus Strains

Eight strains of Kluyveromyces marxianus were screened, and all of them were found to ferment the aldopentose d-xylose directly to ethanol under aerobic conditions. One of these strains, K. marxianus SUB-80-S, was grown in a medium containing 20 g of d-xylose per liter, and the following results were obtained: maximum ethanol concentration, 5.6 g/liter; ethanol yield, 0.28 g of ethanol per g of d-xylose (55% of theoretical); maximum specific growth rate, 0.12 h; 100% d-xylose utilization was completed in 48 h.     

高强度酒精连续发酵

从多株酒精酵母菌株中筛选出S.cerevisiaeKG作为酒精生产菌株。该菌株具有较好的酒精发酵活力和絮凝性。使用具有细胞循环的连续发酵双罐系统,酒精生产强度达到30.5（g／1.h）。根据该系统的动力学模型,讨论了获得高强度酒精连续发酵的途径。     

Aerobic degradation of diethyl phthalate by Sphingomonas sp

An aerobic diethyl phthalate (DEP) degrading bacterium, DEP-AD1, was isolated from activated sludge. Based on its 16S rDNA sequence, this isolate was identified belonging to Sphingomonas genus with 99% similarity to Sphingomonas sp. strain C28242 and 98% similarity to S. capsulate. The specific degradation rate of DEP was concentration dependent with a maximum of 14 mg-DEP/(Lh). Results of degradation tests showed that DEP-AD1 could also degrade monoethyl phthalate (MEP), dimethyl phthalate (DMP), dibutyl phthalate (DBP), and diethylhexyl phthalate (DEHP), but not phthalate and benzoate.     

Invasive infections due to Clavispora lusitaniae

Three cases of Clavispora lusitaniae invasive fungal infections are reported. All three infections appeared in cancer patients presented with fungaemia, one additionally with meningitis. Two of them were breakthrough -- they developed during therapy with conventional amphotericin B with a dose of 0.5 mg kg(-1) day(-1) . All three were cured: two with intravenous fluconazol and one with an increasing dose (1 mg kg(-1) day(-1)) of amphotericin B. In one of two breakthrough cases the sensitivity of the strain to antifungals was tested against antifungal agents and showed in vitro resistance to amphotericin B (MIC 2 eta g ml(-1)).     

Fundamental Studies on the Aerobic Fermentation

The oxygen uptake rate of aggregated mycelia is decreased to an extent which, in the case of a typical spherical aggregate, could be estimated depending on its diameter, mycelial density, oxygen diffusivity, and so forth. Equations were presented in this paper to evaluate the oxygen uptake rate of an mold pellet. A favorable agreement was found between the calculation and the experiment.     

代谢工程改造运动发酵单胞菌用于提高乙醇产量

目的:采用可以在运动发酵单胞菌中表达的操纵子构建重组运动发酵单胞菌,用于提高该细菌对高温高糖的耐受性和提高乙醇产量.方法:用外来的YfdZ、MetB和Hsp构建的多顺反子质粒,转化运动发酵单胞菌而使其获得新的代谢途径.在玉米水解液中,验证了该多顺反子质粒对运动发酵单胞菌产生乙醇的影响.结果:与对照菌相比,在37℃和糖浓度为28%的培养条件下,该基因工程菌的乙醇产量提高到183.2%.在37℃,糖浓度为28%并添加氮源的条件下,该基因工程菌的乙醇产量提高到148.0%.结论:YfdZ、MetB及Hsp三种基因的共同作用能显著提高运动发酵单胞菌的乙醇产量和发酵温度.     

Efficient and Direct Fermentation of Starch to Ethanol by Sake Yeast Strains Displaying Fungal Glucoamylases

Aspergillus oryzae glucoamylases encoded by glaA and glaB, and Rhizopus oryzae glucoamylase, were displayed on the cell surface of sake yeast Saccharomyces cerevisiae GRI-117-UK and laboratory yeast S. cerevisiae MT8-1. Among constructed transformants, GRI-117-UK/pUDGAA, displaying glaA glucoamylase, produced the most ethanol from liquefied starch, although MT8-1/pUDGAR, displaying R. oryzae glucoamylase, had the highest glucoamylase activity on its cell surface.     

燃料乙醇发酵技术研究进展

在分析木质纤维素类生物质制备燃料乙醇原理基础上,重点对燃料乙醇转化过程的发酵工艺进行了论述。目前乙醇发酵工艺主要包括直接发酵、分步糖化发酵、同步糖化发酵、同步糖化共发酵和联合生物加工技术等,对这几种技术的研究现状进行了分析并对其发展趋势进行了展望,通过基因工程构建高效发酵菌种的联合生物加工技术将是未来高效发酵工艺的发展趋势,旨在为有效提高发酵菌株的底物代谢能力,获得高的乙醇产量提供重要参考。     

Aerobic Hydrogen Accumulation by a Nitrogen-Fixing Cyanobacterium, Anabaena sp

Hydrogen evolution by a nitrogen-fixing cyanobacterium, Anabaena sp. strain N-7363, was tested in order to develop a water biophotolysis system under aerobic conditions. A culture of the strain supplemented with carbon dioxide under an air atmosphere evolved hydrogen and oxygen gas, which reached final concentrations of 9.7 and 69.8%, respectively, after 12 days of incubation. Hydrogen uptake activity was not observed during incubation, and nitrogenase was thought to be the sole enzyme responsible for the hydrogen evolution.     

Aerobic versus anaerobic metabolism of halogenated anilines by aParacoccus sp.

AParacoccus sp. which transforms aniline and different halogen-substituted derivatives under aerobic and anaerobic conditions was isolated from the soil. In experiments with¹⁴C-ring-labeled 4-chloroaniline, approximately 60% of the radioactive material disappeared from the growth medium after incubation under anaerobiosis within 48 hr, but under aerobic conditions no decrease of radioactivity in the growth medium was observed, although 4-chloroaniline was completely metabolized. Acetylation appears to constitute, especially under aerobic conditions, a major transformation mechanism by the bacterium, since almost 50% of the acetylated compound could be detected and identified if aniline, 2-, 3-, and 4-chloroaniline served as substrate. The formation of different metabolites under aerobic and anaerobic conditions clearly indicates the existence of two separate pathways in the metabolism of aniline compounds depending on the oxygen status of the environment.     

Industrial Fermentation Ethanol Production in South America

Abstract

Alcohol production from biomass has been of great interest in several countries since the mid 70s due to its potential use as a fuel. This idea, together with internal combustion engines (Otto engines), was born towards the end of the last century. Well into this century several countries used ethanol for mixture with gasoline up to a ratio of 25%. When World War II was over, alcohol lost markets, fossil fuels such as petroleum being economically more viable.     

Fermentation of glutamate by Selenomonas acidaminophila sp. nov.

From an anaerobic digester a novel type of strictly anaerobic, Gram-negative, non-sporeforming mesophilic bacterium was isolated. The cells were curved rods, motile by means of lateral flagella and contained b- and c-type cytochromes. The G+C content of the DNA was 48.0±1.0 mol%. The isolate was able to ferment only glutamate, aspartate, lactate and pyruvate. Organic fermentation products were acetate, propionate and succinate. Propionate was probably formed via a reductive succinate pathway. Strain DKglu16 is described as the type strain of a new species, Selenomonas acidaminophila sp. nov., in the family Bacteroidaceae.Abbreviations atm atmosphere - Pa Pascal - SSC standard saline citrate - G+C guanine+cytosine - _max maximum specific growth rate     

Aerobic reduction of manganese oxide by Salmonella sp. strain MR4

A new isolate of Salmonella, strain MR4, reduced Mn(IV)O₂ at 2.3 mM under aerobic conditions by about 83% over 24 h. Direct contact of cells to MnO₂ was not necessary as the cell-free spent medium produced a similar amount of Mn(II). Pyruvate (1.6 mM) and oxalate (0.8 mM) were identified in the culture medium and presumed to have a role in Mn(II) production in this microorganism.     

Production and Purification of Extracellular D-Xylose Isomerase from an Alkaliphilic, Thermophilic Bacillus sp

An alkaliphilic, thermophilic Bacillus sp. (NCIM 59) produced extracellular xylose isomerase at pH 10 and 50 degrees C by using xylose or wheat bran as the carbon source. The distribution of xylose isomerase as a function of growth in comparison with distributions of extra- and intracellular marker enzymes such as xylanase and beta-galactosidase revealed that xylose isomerase was truly secreted as an extracellular enzyme and was not released because of sporulation or lysis. The enzyme was purified to homogeneity by ammonium sulfate precipitation followed by gel filtration, preparative polyacrylamide gel electrophoresis, and ion-exchange chromatography. The molecular weight of xylose isomerase was estimated to be 160,000 by gel filtration and 50,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, indicating the presence of three subunits. The enzyme is most active at pH 8.0 and with incubation at 85 degrees C for 20 min. Divalent metal ions Mg, Co, and Mn were required for maximum activity of the enzyme. The K(m) values for D-xylose and D-glucose at 80 degrees C and pH 7.5 were 6.66 and 142 mM, respectively, while K(cat) values were 2.3 x 10 s and 0.5 x 10 s, respectively.